Or search by topic
The idea of routes through triangular mazes can be adapted for a range of similar problems.
Is it possible to create different arrangements of numbers to give different families of solutions?
Draw a 'doodle' - a closed intersecting curve drawn without taking pencil from paper. What can you prove about the intersections?
I want some cubes painted with three blue faces and three red faces. How many different cubes can be painted like that?